Fig. 1: Concept of the highly durable crack sensor working in culture media.

a Dimensions of the PDMS-encapsulated crack sensor-integrated silicone rubber cantilever. b Schematic of a silicone rubber cantilever composed of various layers and operation principle of the cantilever sensor-integrated with a PDMS-encapsulated crack sensor to measure the contractile force of cardiomyocytes in liquids. c Nano-patterns used to align the cardiomyocytes on the cantilever surface. d Circuit diagrams of two different crack sensors operating in culture media.